A wind turbine generator, which transmits generated electrical power to a utility grid, is required to contribute to stabilization of the utility grid. In order to stabilize the utility grid, it is necessary to stabilize the frequency (grid frequency) and the voltage (grid voltage) within predetermined ranges.
In order to stabilize the grid voltage, it is necessary to supply or absorb reactive power. It is desired that, as much as possible, supply or absorption of reactive power be performed continuously. Furthermore, when an accident occurs in the utility grid or when the load is increased rapidly, it is desired that supply or absorption of reactive power be performed as quickly as possible.
As devices for performing such supply or absorption of reactive power, reactive power compensators, such as an SVC (static var compensator) and a STATCOM (static synchronous compensator), have been developed and put to practical use. In particular, the STATCOM is capable of performing quick and continuous control of reactive power, which is effective in stabilizing the grid power.
Furthermore, PTLs 1 and 2 describe wind turbine generators including a power converter (inverter) in which a generator power converter connected to a generator and a utility-grid power converter connected to a utility grid are connected with a DC circuit, and the utility-grid power converter is used as a reactive power compensator, to supply reactive power to the utility grid.